Concomitant bovine viral diarrhea, mycotoxicosis, and seneciosis in cattle from northern Paraná, Brazil

Resumo

This study investigated the causes of mortality in cattle from northern Paraná, southern Brazil, during which 9.5% (23/242) of Nellore cows died after clinical manifestations of uncoordinated gait, fever, transient bloody diarrhea, dyspnea, and lateral decumbency. All cattle were maintained on poor pastures, and ingested moldy silage and sprouts of Senecio brasiliensis. Serum samples (n=17) were collected for virus neutralizing (VN) antibodies assays against bovine viral diarrhea virus (BVDV) and bovine herpesvirus 1 (BoHV-1). Three cows were necropsied; fragment of tissue samples collected during necropsy from two cows were used in polymerase chain reaction (PCR) and reverse transcription- PCR assays to identify BoHV-1 and BVDV; blood samples (n=6) were obtained for hematological and biochemical analyses. Significant gross findings of all cows included increased liver consistency, intestinal bleeding, and pulmonary hemorrhage. Histopathology revealed hepatic fibrosis, hemorrhagic enteritis, renal tubular necrosis, pulmonary hemorrhage, and widespread vasculitis. All serum samples contained VN antibodies against BoHV-1, but only four of these reacted positively to BVDV. The RTPCR assays amplified specific amplicons of the untranslated region of BVDV from tissues samples of both animals; direct sequencing and sequence analyses demonstrated that these sequences clustered within the BVDV subgenotype 1d; all PCRs were negative for BoHV-1. Toxicological analyses of the moldy silage demonstrated elevated concentrations of ochratoxin (75.94 ?g/kg). Laboratory evaluations revealed renal and hepatic dysfunctions. These findings confirmed the combined actions of BVDV-1d infection and toxicosis by mycotoxin and S. brasiliensis in cattle mortality at this farm.